Functional group containing cyclic diolefin butyl rubbers

ABSTRACT

Isobutylene-based elastomers containing 3-15 mol percent enchained cyclic diolefin such as cyclopentadiene, and other comonomers such as isoprene, piperylene and butadiene to allow for chemical modification with anhydride, carboxy, hydroxy, etc. to produce a one package through cure system.

This is a continuation, of application Ser. No. 784,656, filed Apr. 4,1977 now abandoned.

BACKGROUND OF THE INVENTION

This invention relates to isobutylene-based polymers containingenchained cyclic diolefin moieties as well as certain functional groupswhich allow chemical and/or physical through curing, while the surfacemay be air dried owing to the cyclic unsaturation.

Isobutylene-based polymers containing relatively low (less than about10%) enchained cyclic diolefin and exhibiting excellent ozone resistanceare well known in the art. See U.S. Pat. Nos. 2,577,822, 2,521,359,2,626,940 and 3,903,039. Isobutylene-based polymers containing greaterthan 10 mol percent cyclic diolefin are also known in the art. See U.S.Pat. No. 2,521,359 and Ind. Eng. Chem. Prod. Res. & Dev. 10, 279(1971).Also see U.S. Pat. No. 3,496,129 which discloses a non-elastomericcyclic diolefin-containing air dryable coating.

Although the above-mentioned polymers have been known for a number ofyears, they have never been commercialized, partly owing topolymerization problems such as reactor fouling, poor catalystefficiency, difficulties in handling the reactive cyclic diolefins andtheir severe molecular weight depressing effect; but the major reasonfor their lack of commercialization has been that attractive propertiesfor practical applications have not been developed.

Butyl-type polymers in general possess many desirable properties forsurface coatings. For example, they have low permeability, excellentchemical resistance, good environmental resistance, low waterabsorption, permanent flexibility and low surface energy to provide goodsubstrate wetting and physical adhesion. Despite these properties, lowmolecular weight butyl-type polymers have had limited commercial successowing to: (1) they can only be used in a two part system (i.e., chemicalcuratives are required); (2) the only ambient condition cure systemavailable is based on quinoid compounds which produce a dark color andare staining so that ambient cured light colored coatings are notpossible; and (3) the coatings have a relatively high degree of surfacetack and become even tackier during exposure so that a high dirt pick-upis always encountered. Despite extensive work of researchers with bothcyclic and acyclic butyl-type polymers the desired combination ofproperties has heretofore never been realized.

SUMMARY OF THE INVENTION

It has surprisingly been found that a tack-free, air dryable, highlyattractive elastomeric coating can now be produced by first preparing abutyl-type polymer containing cyclic diolefin moieties as well asolefinic residues or styrene moieties. Specific functional groups arethen introduced which will allow for a one package, ambient-conditionself-cure to provide a through-cured, light colored, non-tackyelastomeric coating. While one-package cure systems are preferred formost applications, these polymers can also be cured by addition of acurative, and therefore, can also be utilized as a two-package curesystem.

The polymers of the instant invention are suitable for use as coatings,sealants, mastics, caulks, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further illustrated by reference to thedrawings in which:

FIG. 1 shows the effect of diene level on achieving a tack-free surface.

FIG. 2 shows the relationship of film thickness to through-cure.

DETAILED DESCRIPTION

Polymers suitable for use in the instant invention are isobutylene-basedelastomeric polymers containing from about 3 to 15 mol %, preferablyabout 5 to 9 mol % enchained C₅ -C₁₂ cyclic diolefins and from about 0.5to 30 mol % preferably about 0.5 to 10 mole %, most preferably about 0.5to 5 mole % of other monomers capable of producing olefinic residues orstyrene moieties into the backbone of the resulting polymer.Non-limiting examples of such cyclic diolefins include cyclopentadiene,mono- or poly alkylated (where the alkyl groups contain less than 6carbon atoms) cyclopentadienes such as methyl and ethyl cyclopentadiene,1,3-cyclohexadiene and alkylated (where the alkyl groups contain lessthan 6 carbon atoms) analogs, and other materials capable of beingincorporated as a cyclic olefin, such as β-pinene.

Other monomers polymerized into the isobutylene/cyclic diolefin systemare selected depending on desired properties conventionally known in theart. Non-limiting examples of such other monomers suitable for use inthe instant invention are:

Conjugated diolefins represented by the formula ##STR1## where each Rmay be independently hydrogen, an acyclic, or alicyclic hydrocarbonradical having from 1 to 12 carbon atoms, preferably alkyl radicalshaving from 1-6 carbon atoms. Non-limiting examples of such diolefinsinclude isoprene, butadiene, piperylene, 2,3-dimethyl butadiene,2-phenyl butadiene 1,3; 2-methyl hexadiene 1,3; vinyl cyclohexenes.

Non-conjugated diolefins ##STR2## where n=1→4, m=0→4 and the R's aredefined as above, such as: 2-methyl 1,4 pentadiene; 2-methyl1,4-hexadiene; 2,3-dimethyl 1,5-heptadiene, etc. Styrene or substitutedstyrenes or α methyl styrenes ##STR3## where R¹ =H or CH₃ and R isdefined as above, such as: styrene, α-methyl styrene, p-methyl styrene,p-t-butyl styrene, etc.

These other monomers allow for chemical modification by introduction ofspecific functional groups thereby creating a desirable one packagethrough cure system. It is preferable that the other monomer or monomersbe chosen such that they be incorporated as a Type II olefinic residueas opposed to a Type IV olefinic residue such as is present inconventional butyl rubber. The Type II olefinic residue is lesssterically hindered and more reactive than the Type IV olefinic residue,although for some purposes Type IV or Type V olefin residues aresuitable. Examples of what is meant by Type II Type IV and Type Volefinic residue is illustrated below and is based on the BoordClassification described by Schmidt and Boord in J.A.C.S. 54, 751(1932).

Type II olefinic residue ##STR4## as from using butadiene as the diene.

Type IV olefinic residue ##STR5## as from using isoprene as the diene.

Type V olefinic residue

    R.sub.2 C=CR.sub.2

as from using dimethyl butadiene as the diene.

Thus, polymers are prepared by incorporating into the isobutylene/cyclicdiolefin polymer backbone moieties with Type II olefinic structures,through proper selection of the diolefin or by introducing an aromaticnucleus through the use of styrene-based monomers. The desiredfunctional groups to impart the desired through cure characteristics canbe subsequently easily introduced utilizing conventional organicchemical reactions.

The polymers of the instant invention contain from about 60 to 96 mol %preferably about 85 to 95 mol % isobutylene; from about 3 to 15 mol %,preferably about 5 to 9 mol % of cyclic diolefin; and from about 0.5 to30 mol %, preferably about 0.5 to 5 mol % of other monomer discussedabove. The viscosity average molecular weight of the resulting polymersof this invention are from about 10,000 to 700,000, preferably about15,000 to 80,000 and more preferably about 20,000 to 50,000. Thepolymers of the instant invention may be prepared by conventionalpolymerization techniques, such as, cationic polymerization inhomogeneous or heterogeneous (cement suspension) systems.

Functional groups are introduced by reacting the isobutylene/cyclicdiolefin-based copolymer with various compounds selected from thenon-limiting group consisting of maleic anhydride, chlorohydrins,peracids, and sulfuric acid. Preferred are maleic anhydride or peracids.Other conventional olefinic reactions are also suitable, such as:halogenation, addition of nitrosyl chloride, "OXO" reaction, "ene"reaction with formaldehyde, addition of trichlorosilane, "Prins"reaction, oxidative hydrolysis via MnO- or OsO₄ --catalyst, addition ofmercapto acids or alcohols etc.

It is important to note that reactions chosen to introduce the desiredfunctional group must be chosen to be compatible with the reactiveolefin or aromatic nucleus introduced into the polymer backbone duringpolymerization. Sufficient cyclic diolefin functionality must remainafter the chemical modification reaction to permit oxidative surfacecuring in order to produce a non-tacky surface. The most desirablefunctional groups are those which are known to permit "one package"through cures at ambient conditions without undesirable side reactionsor color. These functional groups are preferably anhydride, carboxy,hydroxy, silane, mercapto, and sulfonic acid, although other functionalgroups such as epoxy, halogen, etc. may be desirable and useful incertain applications.

The essence of the instant invention described herein is the concept ofcombining the oxidative surface cure provided by cyclic diolefins with adesired one package preferably ambient-condition through cure anddesirable adhesion characteristics provided by the introduction ofselected functional groups. This invention may best be illustrated bythe following non-limiting examples.

EXAMPLE 1

A typical low molecular weight butyl polymer was prepared bycopolymerizing isobutylene and isoprene according to the methods of U.S.Pat. No. 3,562,804 incorporated herein by reference. The polymer had anMv of 32,000 and an INOPO of 28; it contained 4.1 mole % isoprene. INOPOrepresents the iodine number, the procedure for which is taught inIndustrial and Chemical Engineering, 17, 367, (1945). A coatingmasterbatch was prepared by mixing together the following ingredients togive a uniform coating composition:

    ______________________________________                                        Polymer               100 parts                                               Toluene               25 parts                                                Calcene TM.sup.1      30 parts                                                Hi Sil 233.sup.2      10 parts                                                Titanium Dioxide      10 parts                                                Stearic Acid          1 part                                                  Zinc Oxide            5 parts                                                 ______________________________________                                         .sup.1 A calcium silicate                                                     .sup.2 A hydrated silica                                                 

The masterbach was divided into aliquots, compounded with variousamounts of curatives, and then cast into films and cured for evaluationas an elastomeric coating. The curative system in each case consisted of7.5 phr of PbO₂ added as a paste in dibutyl phthalate and varyingamounts of paraquinone dioxime (GMF). This curative system was used inall formulations since it is the only one known to be capable of curinglow molecular weight isoprene butyls at ambient conditions. The castfilms were cured for 7 days at room temperature followed by 7 days at158° F. to yield fully cured films for evaluation. Measured physicalproperties at various GMF levels are tabulated below:

    ______________________________________                                        GMF (phr)       1.5       3.0       6.0                                       Tensile, psi    190       240       255                                       Elongation, %   660       480       400                                       ______________________________________                                    

The cured films were resilient with acceptable physical properties andshowed good through cure as shown by low extractability in solvents.However, in spite of the use of white pigments to try to achieve a lightcolored coating, they were all fairly dark brown in color owing to thecuratives and all films showed a high degree of surface tackiness. Theyall showed a very high degree of dirt pick up during outdoor exposuretesting and were generally aesthetically unattractive as coatings. Thesurface of the films also tend to soften and become even more tackyduring exposure to further negate usefulness in exposed coatings whereaesthetic appeal is necessary.

Attempts to overcome the disadvantageous properties of these coatings bycompounding with other fillers and additives proved largely futile.

EXAMPLE 2

A series of low molecular weight butyl polymers were prepared bycopolymerizing isobutylene with varying amounts of isoprene to determinewhether raising the unsaturation level would enable non-discoloringambient temperature cure systems to be used and would diminish thetackiness and dirt pick up problems. The polymers were synthesized withan Mv of about 20,000 and with INOPO's ranging from 8 to 30(corresponding to mole % isoprene ranging from 1.2 to 4.5). Polymers ofsignificantly higher INOPO are difficult to prepare with isoprene as thediene because butyls produced at higher isoprene contents are branchedand contain gel (cross-linked polymer). These high isoprene butyls causerapid reactor fouling during polymerization and are unattractive incoatings because of the high gel content.

None of these polymers were curable at ambient temperature with any ofthe typical non-staining curative systems which are used in othercommercial elastomeric coatings; therefore all coatings evaluations wereconfined to the quinoid (GMF) cure system. Our studies showed thatfurther increases in unsaturation, beyond a minimum unsaturationrequired to allow network development to occur during cross-linking,were of little or no benefit in improving either the properties or theperformance of the polymers in coatings. Physical properties ofvulcanized films prepared from this series of polymers and cured to aconstant elongation at break of 400%, by adjusting the GMF level, aretabulated below:

    ______________________________________                                        PHYSICAL PROPERTIES OF VULCANIZATES CURED                                     TO 400% ELONGATION-AT-BREAK                                                          Mole %    Tensile,  200% Modulus                                                                             Surface                                 INOPO  Isoprene  psi       psi        Tack                                    ______________________________________                                         8.6    1.25     122       25                                                 12.9   1.9       109       22                                                 14.9   2.2       122       24         all                                     18.0   2.7       124       25         very                                    20.6   3.0       117       23         tacky                                   26.7   4.0       116       26                                                 28.4   4.2       119       29                                                 29.9   4.3       116       27                                                 30.2   4.5       120       27                                                 ______________________________________                                    

Raising the unsaturation level enabled vulcanization to be effected at alower curative level but did not improve physical properties at a fixedelongation-at-break and did not diminish surface tackiness or tackdevelopment and dirt pick up during outdoor exposure. Tackiness and highdirt pick up persisted even when the more highly unsaturated polymerswere cured to a tighter network (with too low an elongation for mostelastomeric coating applications) by using higher levels of GMF.

These examples show that a conventional isoprene type low molecularweight butyl rubber does not lead to a non-tacky, ambient condition,through-cure system and is unable to produce aesthetically attractive,light colored, durable elastomeric coatings.

Similar results were obtained with butadiene, piperylene, dimethylbutadiene, and other similar dienes as the comonomer showing thatconventional low molecular weight butyls are not suitable for thosecoating applications where low dirt pick up and aesthetic appeal arerequired.

EXAMPLE 3

Since conventional low molecular weight butyl rubbers were not suitableas light colored, low dirt pick up elastomeric coatings, a series offunctional group-containing low molecular weight butyl rubbers wereprepared. This was done by introducing functional groups, intoconventional butyl rubber by use of various reagents. These functionalgroup-containing butyl rubbers were then evaluated as elastomericcoatings. In particular chlorine was introduced into a low molecularweight isoprene butyl rubber by the methods taught in U.S. Pat. No.2,944,578. These functional group-containing isoprene butyl rubbers wereformulated into coating compositions, applied, and evaluated todetermine whether aesthetically attractive and during elastomericcoatings could be prepared. The results, as summarized for chlorinebelow, show that by introducing other functional groups, light-colored,cured, elastomeric coatings can be prepared. Unfortunately thisnevertheless, does not overcome the tackiness and dirt pick up problems.Hence, simple functional group-containing conventional butyl rubbers arealso not suitable for coating applications where low dirt pick up andaesthetic appeal are required.

Chlorinated low molecular weight butyl as an Elastomeric Coating

The low molecular weight isobutylene/isoprene copolymer of Example 1with an Mv of 32,000; an INOPO of 28; and containing 4.1 mole % ofisoprene was chlorinated by the methods of U.S. Pat. No. 2,944,578 toyield a modified low molecular weight butyl rubber containing 3.1 wt. %chlorine, hereinafter referred to as LM Chlorobutyl.

This LM Chlorobutyl was readily cross-linkable at room temperature witha variety of cure systems as shown below:

    __________________________________________________________________________    GUM CURES OF LM CHLOROBUTYL AT ROOM TEMPERATURES                                       1             2             3                                        __________________________________________________________________________    Cure System                                                                            LM Chlorobutyl                                                                         100 parts                                                                          LM Chlorobutyl                                                                         100 parts                                                                          LM Chlorobutyl                                                                         100 parts                                Dibutyl Tin   Butyl Tin tri-                                                                          5   Oxydibenzyl                                       Sulfide   6   chloride      Mercaptan                                                                               9                                       SnCl.sub.2 . 2H.sub.2 O                                                                 5   Dibutyl Tin                                                                             4   SnCl.sub.2 . 2H.sub.2 O                                                                 5                                                     Sulfide                                                Cure Time (Days)                                                              @R.T.    1        19   1        19   1        19                              100% Mod. psi                                                                          20       120  230      --   50       --                              Tensile Strength,                                                                      40       410  680      700  140      830                             psi                                                                           Elongation, %                                                                          1400     29   290      60   290      80                              __________________________________________________________________________

Good elastomeric networks were readily achieved and cure rate wasreadily controlled by varying the curatives; however, all the curedfilms were very tacky. A series of filler loaded films were preparedusing cure system (2) to determine whether physical properties andtackiness of the filled films would be attractive for elastomericcoatings. The formulation used for this series of tests was:

    ______________________________________                                        LM Chlorobutyl         100 parts                                              Filler                 as shown                                               Butyl Tin Trichloride   5                                                     Dibutyl Tin Sulfide     4                                                     ______________________________________                                    

The formulations were prepared in a Baker Perkins minikneader andpressed into 20 mil pads for curing and evaluation. Pads were cured for15 minutes at 195° F. which tests showed was sufficient to develop afully cured network. Results are summarized below:

FILLED LM CHLOROBUTYL VULCANIZATES

    ______________________________________                                        FILLED LM CHLOROBUTYL VULCANIZATES                                                                Tensile                                                                       Strength                                                  Filler       PHR    psi      Elongation,%                                                                           Tackiness                               ______________________________________                                        Atomite.sup.1                                                                              50     200      290                                              Asbestine 325.sup.2                                                                        50     275      230                                              Whitetex Clay                                                                              50     250      230      All                                     McNamee Clay 50     240      280      very                                    Purecal U.sup.3                                                                            50     420      340      tacky                                   Mistron Vapor Talc                                                                         50     500      310                                              Suprex Clay  50     410      340                                              Hi Sil 233   40     800      360                                              ______________________________________                                         .sup.1 Calcium carbonate                                                      .sup.2 a shortfibered asbestos filler                                         .sup.3 calcium carbonate                                                 

The filled vulcanizates were all light-colored and possessed acceptablephysical properties for elastomeric coatings, but all were very tacky.Tackiness was not eliminated by increasing the filler loading until theloading was so high that the films became weak, cheesy, andnon-elastomeric.

When solvent-based coatings were formulated from this LM Chlorobutyl andevaluated, similar results were realized. At modest filler loadings thecoatings were tough, white and elastomeric but were tacky and showedhigh rates of dirt pick up. At higher loadings they became weak andcheesy with high rates of chalking. It was not possible to achieve thedesired goal of a non-tacky tough coating which would make anaesthetically attractive, durable, elastomeric coating.

This work shows that simply introducing functional groups intoconventional butyls does not overcome all the problem areas noted anddoes not enable the desired elastomeric coatings to be produced. Inparticular the introduction of functional groups does not satisfactorilyeliminate the inherent tackiness and dirt pick up properties ofconventional butyls.

EXAMPLE 4

Since isobutylene copolymers containing certain cyclic dienes were knownto cure oxidatively to produce dry non-tacky surfaces, a series of lowmolecular weight butyl rubbers containing various amounts ofcyclopentadiene (CPD) or methyl cyclopentadiene (MCPD) were prepared andevaluated in an effort to develop a butyl copolymer which would besuitable for non-tacky elastomeric coatings with low dirt pick upproperties. This series of copolymers were first evaluated to determinethe cyclic diene content required to produce a tack-free surface. Thecopolymers were compounded in the following simple coating formulations:75 phr Nytal 300, 20 phr Hi-Sil 422, 20 phr TiO₂, 1 phr 6% CobaltNaphthenate, xylene to workable viscosity. The coatings were drawn downon a Mylar film with a 50 mil applicator to yield dry coatings 15-18mils thick. The coatings were allowed to air cure at ambient conditionsin the laboratory and evaluated daily for tackiness. Results of thisevaluation are plotted in FIG. 1. The data show that greater than 10mole % cyclic diene is required to achieve a tack-free surface even withvery long exposure and 15 mole % cyclic diene is required to reach thetack-free state within several days of drying. The cut off is quitesharp.

The copolymers containing enough cyclic diene to achieve a tack-freesurface were evaluated more completely for suitability in coatings.Typical results of these evaluations are summarized in Tables 1 and 2.An evaluation of CPD Butyl LM coatings as thick (15-18 mil) films isshown in Table 1. The films developed tack-free surfaces relativelyquickly but were completely unsuitable as elastomeric coatings. They hadlow elongations and were generally cheesy being easily broken andscratched off with the fingernail. Furthermore, they were very poorlythrough-cured as shown by their being 70 to 90% soluble after 14 dayscuring. Even after 500 hours in the weatherometer the films were stillweak, cheesy and non-elastomeric. Further, at the higher CPD contentsthey showed surface cracking and checking in the weatherometer whileremaining soft and cheesy beneath the hard brittle surface.Through-cures were not developed even after 500 hours in theweatherometer.

                  TABLE 1                                                         ______________________________________                                        PERFORMANCE OF HIGH UNSATURATION CPD                                          BUTYL LM IN THICK FILMS                                                       Sample         A       B        C     D                                       ______________________________________                                        Mv (estimated) 20,000  20,000   16,000                                                                              25,000                                  CPD, mole %.sup.c                                                                            11      19       19    28                                      IP, mole %.sup.c                                                                             0       0        8     0                                       Coating.sup.d :                                                               Tack-free, days.sup.e                                                                        2       <1       <1    <1                                      Tensile, psi.sup.f                                                                           145     150      76    81                                      Elongation, %.sup.f                                                                          69      15       48    ˜30                               Percent Insolubles.sup.f                                                                     24      30       34    10                                      500 Hr. Weatherometer                                                         Exposure.sup.g                                                                Tensile, psi   340     187      212   187                                     Elongation, %  48      50       61    ˜50                               Film Appearance                                                                              Cheesy  Cracks,  Check-                                                                              Cheesy,                                                        Cheesy   ing,  V.soft                                                                  Cheesy                                                                              Below                                                                         Surface                                 ______________________________________                                         .sup.c By NMR. IP = Isoprene CPD =                                            .sup.d Coating Formulation: 150 phr Nytal 300, 20 phr Titanox RANC, 1 phr     6% Cobalt Naphthenate, 127-240 phr Xylene (for brushing consistency).         .sup.e Air cured at ambient laboratory conditions.                            .sup.f Coating drawn down on Mylar with 50 mil applicator to give dry         thickness of 15-18 mils. Microtensiles pulled after 14 days, at 10            in./min. Films are not elastomeric.                                           .sup.g Sunshine arc, 102 min. dry, 18 min. spray.                        

Results of this thick-film evaluation showed that the CPD-containingbutyls are not desirable as elastomeric coatings and that lack ofthrough-cure may be at least partly responsible for their poorproperties. A study was therefore made with coatings prepared from aButyl LM polymer with 13 mole % CPD to determine how the extent ofcrosslinking depends upon film thickness. Films were drawn down atvarious thicknesses and then tested for solubility after 14 and 33 daysair-cure at ambient conditions. The data summarized in FIG. 2 show thatthe CPD-containing polymers do not through-cure. Percent insolublepolymer is strongly dependent upon film thickness and even after longexposure only the surface of the films is crosslinked. Thus thin filmswith a high surface/volume ratio are largely insoluble while the thickerfilms with more non-surface volume remain largely uncured. The thinfilms become hard and brittle while the thicker films develop a hardsurface, but remain soft and cheesy underneath. Apparently oxygen is notable to diffuse through the cured surface layer of these films to effecta through-cure.

                  TABLE 2                                                         ______________________________________                                        PERFORMANCE OF HIGH UNSATURATION CPD                                          BUTYL LM IN THIN FILMS                                                        Coating.sup.a A       B        C      D                                       ______________________________________                                        Hardness.sup.b, 10 Month                                                      Cure          5B      2B       B-2B   4B                                      Color         Yellow  Yellow   Yellow White                                   Outdoor Exposure.sup.c                                                        Dirt Pickup Resistance                                                        1.3 Mo.       Fair    Good     Good   Good                                    3.5 Mo.       Poor    Good     Good   Good                                    6 Mo.         Poor    Good     Good   Good                                    Chalking                                                                      3.5 Mo.       None    Medium   Medium Medium                                  6 Mo.         None    Medium   Medium Medium                                  10 Mo.        None    Medium   --     Medium                                  Hardness.sup.d, 6 Mo.                                                                       Fair    Good     Good   V.Good                                  Weatherometer                                                                 Exposure.sup.e                                                                Chalking                                                                      500 hrs.      None    None     None   Medium                                  730 Hrs.      None    Light    Medium Heavy                                   1730 Hrs.     Heavy   Heavy    Heavy  Heavy                                   ______________________________________                                         .sup.a The polymers used in these coatings and their properties are shown     in Table 1.                                                                   .sup.b Pencil hardness, 10 month curing indoors.                              .sup.c In Linden, N.J., 45° , South, starting in May, 1971.            .sup.d Resistance to fingernail scratch.                                      .sup.e Sunshine arc, 102 min. dry, 18 min. spray.                        

Although this work shows that the CPD-butyls are obviously unattractiveas thick elastomeric coatings, a further evaluation was conducted withthe same coatings discussed in Table 1 but this time as thin paint filmswhere good through cure could be expected because of the very highsurface to volume ratio. Results of this thin film evaluation aresummarized in Table 2. The copolymers were also unattractive as thinpaint films. At low CPD content the film remained fairly soft and showedhigh dirt pick up, but was fairly resistant to chalking. At the higherCPD levels, dirt pick up resistance was improved but chalking becamesevere. None of the coatings were elastomeric.

Clearly the CPD-containing copolymers are unacceptable for exposedelastomeric coatings with low dirt pick up and aesthetic appeal. Similarconclusions were drawn from evaluation of MCPD-containing copolymers orfrom terpolymers containing isoprene, isobutylene and cyclic diene.

EXAMPLE 5

Although higher molecular weight polymers are less attractive in solventbased coatings because they require too much dilution with solvent toreduce viscosity to a workable level, a series of cyclicdiene-containing butyl rubbers with 2 to 3 times the molecular weight ofthose evaluated in Example 4 were prepared and evaluated to see ifbetter coating properties could be achieved with the higher molecularweight polymers. Evaluations on these higher molecular weight polymersare summarized in Table 3.

                                      TABLE 3                                     __________________________________________________________________________    PERFORMANCE OF CPD AND MCPD POLYMERS IN AIR-DRY COATINGS.sup.a                (THICK FILMS)                                                                 Polymer Composition Mole %                                                                   Tack    Cure after 14 Days Air-Dry                             CPD  IP   --Mv 2 days                                                                            13 days                                                                           Tensile,psi                                                                         % E                                                                              % Insolubles                                                                         Comments                               __________________________________________________________________________    13   0    40,000                                                                             Slight                                                                            None                                                                              169   68 11                                            13   0    64,000                                                                             None                                                                              None                                                                              284   58 20                                            13   4    56,000                                                                             None                                                                              None                                                                              278   78 22     All                                    MCPD                                   films                                  7    4    48,000                                                                             Very                                                                              Almost                                                                             72.sup.d                                                                            45.sup.e                                                                        7      cheesy and                                            Slight                                                                            none                not                                    8    0    72,000                                                                             Very                                                                              Almost                                                                             136.sup.d                                                                           60.sup.e                                                                        6      elastomeric                                           Slight                                                                            none                                                       9    5    52,000                                                                             Very                                                                              Almost                                                                             122.sup.d                                                                           50.sup.e                                                                        8                                                            Slight                                                                            none                                                       __________________________________________________________________________     .sup.a 75 phr Nytal 300, 20 phr HiSil 422, 20 phr TiO.sub. 2, 0.06 phr        Cobalt (as metal). Dry film thickness was about 15 mils.                      .sup.d Tensile at yield point                                                 .sup.e Elongation at yield point.                                        

No significant improvement in the coatings resulted from increasing themolecular weight. The films become tack-free or nearly so but were notelastomeric. As thick films they remained soft and cheesy with a hardsurface layer--and they showed poor through-cure characteristics asevidenced by the high solubles content. They also performed poorly whenevaluated as thin paint films. After 20 weeks air-dry indoors the filmswere still cheesy and easily broken with a fingernail. After 6 monthsoutdoor exposure the films were becoming brittle and were chalkingbadly. Clearly these non-functional group containing cyclic diene butylsare unacceptable as elastomeric coatings.

Examples 1-5 show that one is not able to achieve the desiredaesthetically attractive non-tacky, tough, durable and elastomericcoatings with conventional butyl rubbers, with functionalizedconventional butyl rubbers, or with isobutylene/cyclic diolefincopolymers containing only olefinic functionality. None of thesepolymers is capable of giving a non-tacky surface and a good elastomericthrough-cure at the same time so that substantial efforts to develop thedesired elastomeric coatings based upon these polymers have alwaysfallen short of the goal.

EXAMPLE 6

A terpolymer was prepared from cyclopentadiene, isoprene, andisobutylene. This had an Mv of 26,500 and contained 6 mole percent CPDand 7 mole percent isoprene. 136 g. of this polymer was treated with11.7 g. of maleic anhydride and heated with agitation for 15 hours at185° C. The product was dissolved in toluene to form a 50% cement, andthis was centrifuged to remove unreacted maleic anhydride.

The product had an Mv of 27,800 and contained 2.2 mole percent anhydridegroups according to the saponification number.

A zinc oxide paste was prepared by dispersing 500 g. ZnO (Protox 166)with 237.5 g. Varsol 18 and 12.5 g. of an 80% Butyl LM 430 cement intoluene, in a pebble mill. The 50% solution of the maleic anhydrideadduct was then compounded as follows:

16.3 g. 50% solution of maleic anhydride adduct in toluene.

2.8 g. ZnO paste

0.9 g. Varsol #2¹

0.28 g. Tributylamine

These ingredients were mixed together to form a uniform coating. A15-mil (dry film thickness) film was cast and allowed to cure at ambientconditions (75° F., 60% Rel. Hum.). This film cured overnight, resultingin a white, elastomeric coating. Tensile properties measuredperiodically are as follows:

    ______________________________________                                        Days Cured                                                                               3             8             15                                     Tensile, psi                                                                            260           360           400                                     Elongation, %                                                                           150           140           160                                     ______________________________________                                    

The surface of the film was essentially tack-free after 2 days. The filmhad acceptable physical properties for an elastomeric coating and waswhite and tack-free with a good through cure.

EXAMPLE 7

A cement consisting of 33.1 g. of a terpolymer of isobutylene, isoprene(5.8 mole %) and cyclopentadiene (7.3 mole %), 33.1 g. Varsol 18 and10.0 g. of chlorobenzene was treated successively at 85° C. with 0.17 g.Irganox 1010, 2.85 g. of maleic anhydride and 0.33 g. benzoyl peroxide.The temperature was raised to 100° C. and maintained there for 3 hours.After 45 minutes the mixture becamse extremely viscous and an additional15 g. Varsol 18 was added.

The polymer was formulated into a coating with ZnO as in Example 1. Afilm was cast from this coating, which cured overnight at ambientconditions (75° F., 50% rel. hum.). The film was resilient and tack-freeas desired for an aesthetically attractive elastomer coating.

EXAMPLE 8

A cement consisting of 50 g. of an isobutylenecyclopentadiene (9.7 mole%) copolymer 135 g. Varsol 18, and 15 g. chlorobenzene was treatedsuccessively with 0.25 g. Irganox 1010, 4.3 g. maleic anhydride and 1.5g. of benzoyl peroxide at 85° C. The temperature was increased to 100°C. and maintained there for 3 hours. A coating, similar to the examplesabove, cured to give a resilient and tack-free film. High qualityelastomer coatings could be prepared with this composition as thebinder.

Examples 6-8 show that isobutylene based polymers containing bothcyclopentadiene and maleic anhydride functionality are capable of givinga good elastomeric through cure and a dry non-tacky surfacesimultaneously. These new polymers containing two types of functionalitycan be formulated to give the desired aesthetically attractive,non-tacky, tough, durable, elastomeric coatings.

EXAMPLE 9

A terpolymer was prepared from methylcyclopentadiene (MCPD), isoprene,and isobutylene. This terpolymer had an Mv of 55,000; and Mn (VPO) of20,000; and an INOPO of 30. It contained about 7 mole % diene by NMR ofwhich ˜4 mole % was MCPD. 514 g. of this terpolymer was dissolved in 786g. of hexane to form 1300 g. of a 43.4% cement and then converted to thechlorohydrin by reacting with freshly prepared hypochlorous acid asfollows:

The hypochlorous acid was prepared by bubbling 46.5 g. Cl₂ slowly (overthe course of 221/2 minutes) into 65.5 g. of 50% NaOH in 412 g. ofdistilled water while stirring @-10° C. The freshly preparedhypochlorous acid solution was poured slowly into the 1300 g. of cementwith rapid stirring in a dispersator stirred vessel while maintainingtemperature at 30°-35° C. by adding ice directly to the mixture. Priorto the addition of the hypochlorous acid, the cement had been acidifiedby the addition of 490 ml. of 1 N HCl solution. The mixture was allowedto stir for 30 minutes and then the polymer was recovered by first waterwashing to deash and then drying under vacuum to remove the solvent andrecover the dried modified polymer. The recovered polymer had an Mv of50,000, an INOPO of 20, and it contained 3.8 wt. % chlorine and showed astrong hydroxyl absorption in the infrared spectra.

The polymer was compounded with 50 phr of SRF black in a kneader andthen 9 phr of toluene diisocyanate (T.D.I.) and 0.2 phr of Arkam weremixed in as curatives and a pad was pressed from the compounded polymerat room temperature. After 6 days at room temperature, stress-strainproperties were evaluated. The pad was only slightly tacky and had atensile of 300 psi with an elongation of 200%. It would be suitable foruse as a low tack elastomeric coating. This example shows that anisobutylene-based polymer containing both methyl cyclo-pentadiene andmodified to contain hydroxy functionality is capable of giving a goodelastomeric through-cure and a dry non-tacky surface simultaneously.

As indicated, this particular polymer containing only 4 mole % methylcyclopentadiene does not quite develop a non-tacky surface and at fillerloadings where it remains elastomeric a slight surface tackiness isdetectable. For complete elimination of surface tackiness it ispreferred that the cyclic diene content be above 5 mole %. At less than3 mole % cyclic diene severe surface tackiness and very high dirt pickup is evident. Surface tackiness impressively diminishes as cyclic dienecontent is increased through the range 3 to 5 mole %. At 4 mole % as forthe polymer of this example a slight surface tackiness persists atfiller loadings which five an elastomeric film.

EXAMPLE 10

A terpolymer was prepared from cyclopentadiene (CPD), styrene, andisobutylene. This terpolymer had an Mv of 29,000 and an INOPO of 75. Itcontained 14.8 mole % CPD and 17.5 mole % styrene by NMR analyses.

710 g. of this polymer was dissolved in 860 g. of toluene to yield 1570g. of a cement and then converted to the chlorohydrin by reacting withhypochlorous acid formed "in situ" as follows:

70 g. of conc. (37%) HCl was diluted with 210 g. of distilled water andadded to the cement in a nitrogen-purged stirred resin flask. Then 80.5g. of 30% hydrogen peroxide was diluted with 210 g. distilled water andallowed to drop slowly into the cement from a dropping funnel with rapidstirring. After all the H₂ O₂ was in, the cement was heated to refluxand allowed to stir at reflux (85° C.) for 6 hours. Then 100 g. of 50%NaOH solution was added and the refluxing continued for 1/2 hour more.The modified cement was cooled, deashed by water washing in a separatoryfunnel and then the polymer was recovered by being precipitated in IPOHand dried in a vacuum oven at 180° F.

The recovered polymer had an Mv of 40,000 (some increase in molecularweight had occurred probably due to slight crosslinking during drying).It contained 1.02% chlorine and showed a very strong hydroxyl absorptionin the infrared. It was compounded with 50 phr of SRF black as inExample 4 and then 10 phr of T.D.I. and 0.5 phr of Arkam were added ascuratives and a pad was pressed from the compounded mixture at roomtemperature. After 6 days at room temperature, the pad was relativelyhard and tack free but still very flexible. It had a tensile strength of600 psi with an elongation at break of 100%. It would be suitable foruse as an elastomeric, tack-free coating, but the elongation of only100% would be borderline for many applications. The short elongation andincrease in molecular weight during drying (incipient cross-linking) areboth indicative of excessive functionality. A cyclopentadiene content of15% is about the upper limit which is desired for elastomeric coatingswith reasonably good cured elonation.

This example does show though that isobutylene based polymers containingthe proper amount of cyclopentadiene and hydroxy functionality arecapable of good elastomeric through-cure while simultaneously developinga dry, non-tacky surface. The hydroxy functionality in the modifiedpolymers of Examples 9 and 10 was actually a chlorohydrin structure.This functionality can be introduced into suitable butyls either by theuse of H₂ O₂ /HCl as in Example 10 or by the use of freshly preparedhypochlorous acid as in Example 9. The hydroxy group of the polymericchlorohydrin structure may be used directly in cross-linking withisocyanates, titanate esters etc. to yield an elastomeric through-cure.Alternately, the chlorine may be replaced with another hydroxyl group,forming a glycol, also amenable to crosslinking with isocyanates,titanate ester, etc.

EXAMPLE 11

A copolymer of cyclopentadiene and isobutylene was prepared. Thiscopolymer had an Mv of 17,000; and Mn (VPO) of 8100; and an INOPO of 52.It contained 11 mole % CPD by NMR analyses. 1335 g. of this copolymerwas dissolved in 1630 g. of hexane to yield 2965 g. of a 45% cement andthen converted to the epoxide derivative as follows:

The cement was chilled with stirring in a nitrogen-purged resin flask to12° C. and then 89.7 g. of acetic anhydride and 8 g. of 50% sulfuricacid were added with stirring followed immediately by the dropwiseaddition (over the course of 1 hour) of 199.2 g. of 30% hydrogenperoxide. The mixture was stirred cold for 2 hours and then heated toreflux (at 62° C.) for 2 more hours. It was then cooled and deashed bywater washing in a separatory funnel. The washed cement was diluted withtoluene and then stripped to a boiling point of 110° C. through a shortpacked column to remove all water and hexane and yield a 50% solution ofthe modified polymer in toluene.

A sample of the polymer was recovered by drying the cement in a vac-ovenat 180° F. It had an Mv of 40,000 (some crosslinking occurred during thedrying) and had a strong epoxide absorption in the infrared spectrum.

Into a portion of the cement, 4.5 phr of diethylene triamine was stirredand a portion of this compounded cement was capped and stored. It gelledwithin 6 hours. Another portion of this compounded cement was cast intoa film on glass and allowed to dry. It cured overnight to yield aresilient tack-free and insoluble coating which could not be removedfrom the glass for testing because of the strong adhesion. It would makea very desirable elastomeric coating.

The epoxide used in this example may be prepared by oxidation of theolefin with a peracid such as performic acid, peracetic acid, orm-chloroperbenzoic acid. The epoxides may be reacted with polyols orpolyamines to crosslink, or with dilute HCl to form chlorohydrins, orwith dilute base to form glycols. This example shows that anisobutylene-based polymer containing cyclopentadiene and modified tocontain epoxy groups is capable of giving a good elastomericthrough-cure while simultaneously developing a dry non-tacky surface.

EXAMPLE 12

A terpolymer of cyclopentadiene (CPD), isoprene, and isobutylene wasprepared. This terpolymer had an Mv of 19,000 and an INOPO of 47. Itcontained 5.7 mole % CPD and 4.8 mole % isoprene by NMR analyses. 333 g.of this terpolymer was dissolved in 594 g. of hexane to yield 927 g. ofa 36% cement and then converted to the hydroxyl derivative as follows:

The cement was chilled with stirring in a nitrogen-purged resin flask to13° C. and then 82.7 g. of 20% fuming sulfuric acid (oleum) was addeddropwise from a dropping funnel over the course of 25 minutes. Themixture was allowed to warm with stirring to room temperature and then1500 ml. of distilled water was added along with 500 ml of isopropylalcohol to break the emulsion that formed and keep the mixture fluidenough to stir. The mixture was heated to reflux at 60° C. and stirredat reflux for 1/2 hour. It was then cooled and washed with water in aseparatory funnel to deash. The polymer was recovered by precipitationfrom isopropyl alcohol and then drying in a vacuum oven at 180° F. Therecovered modified polymer had an Mv of 15,000 and showed a stronghydroxyl absorption in the infrared.

It was compounded with 50 phr of SRF black in a kneader as in Example 4and then 7 phr of T.D.I. and 0.25 phr of Arkam were mixed in ascuratives and a pad was pressed from the compounded polymer at roomtemperature. After 6 days at room temperature, stress-strain propertieswere evaluated. The pad was almost completely tack free with a tensilestrength of 180 psi and an elongation of 150%. It would be suitable asan elastomeric tack-free coating in applications requiring a high solidsapplication with only modest strength requirements. The low molecularweight of this modified terpolymer permits formulating into very highsolids coatings with good application properties.

Reaction with sulfuric acid followed by hydrolysis in the classicalmanner introduces a hydroxyl group (i.e., alcohol synthesis from olefinsvia sulfate ester).

Examples 6 through 13 show that isobutylene-based polymers containingthe proper amount of enchained cyclic diolefin (i.e. 3-15 mole %) andmodified to contain other functional groups which allow through-curingare capable of simultaneously developing a dry non-tacky surface(through surface oxidative cross-linking of the cyclic unsaturation) anda good elastomeric through-cure. These polymers can be formulated togive very desirable aesthetically attractive, non-tacky, tough, durable,and elastomeric coatings.

What is claimed is:
 1. A tack-free, air dryable, self-curing elastomericterpolymer coating having a viscosity average molecular weight of about15,000 to 80,000 which consists essentially of about 85 to 95 mol %isobutylene, about 5 to 9 mol % C₅ -C₁₂ cyclic diolefin and about 0.5 to5 mol % conjugated diolefin represented by the formula ##STR6## whereeach R is are independently hydrogen or acyclic or alicyclic hydrocarbonradicals having from 1 to 12 carbon atoms and wherein the terpolymer hasattached thereto a functional group selected from the group consistingof anhydride, carboxy or hydroxy said coating being self-curing throughsurface oxidative crosslinking of said cyclic diolefin.
 2. Thecomposition of claim 1 wherein the cyclic diolefin is cyclopentadiene.3. The composition of claim 1 wherein the cyclic diolefin is a mono orpolyalkylated cyclopentadiene wherein each alkyl group contains lessthan 6 carbon atoms.
 4. The composition of claim 2 wherein the mono orpolyalkylated cyclopentadiene is selected from the group consisting ofmethyl cyclopentadiene, ethyl cyclopentadiene and1,3-dimethylcyclopentadiene.
 5. The composition of claim 1 wherein theconjugated diolefin is selected from the group consisting of isoprene,butadiene and piperylene.
 6. The composition of claim 1 wherein thecyclic diolefin is cyclopentadiene.
 7. The composition of claim 6wherein the functional groups are anhydride.